null is not an object error

I am getting an error on every page in my admin..not on the blog itself but in every admin page like when im posting or stuff.

I get the following error.. Can you tell me how to fix it?
I have tried reinstalling everything as well as just replacing the admin pages but nothing seems to work.

error is as follows:
line 24
car 3
error ‘Null’ Null is not an object
code 0
then the ulr of the page

this is happening on every page when im in the admin.
Help please